The invention relates generally to arthroplastic implants and, more specifically, to the restoration of total knee replacement (TKR) components as an alternative to total knee revision.
Osteoarthritis is defined as a noninflammatory degenerative joint disease occurring chiefly in older persons. Often, as a consequence of joint deterioration, it becomes advisable or necessary to replace the joint, such as hip, shoulder or knee, for example, with an artificial one. The surgical procedure involved is termed arthroplasty and is widely known and used.
Where the knee is the joint involved, the procedure entails the implantation of prosthetic components designed to reproduce the anatomic movement of the knee and the procedure is termed total knee replacement (TKR).
The artificial implants, or prosthetic components in a total knee replacement are ordinarily constructed of a metal alloy, with some components also incorporating a layer of plastic material to provide a smooth articulating surface.
The metal joint components are very strong, being secured to the bone by fixation studs and special adhesives, and are resistant to surface abrasion and scratching except where metal to metal contact occurs.
The plastic components used in conjunction with the metal components do not wear as well as the metal. Owing to this fact, the plastic material often wears through and metal to metal surfaces come into contact, with resultant scratching or abrasion of the metal components.
This problem especially seems to arise with the patellar component, a button-shaped element which can be made of plastic material but with a metal backing. As the knee is flexed, the metal femoral component can eventually wear away the adjacent plastic layer of the artificial patella and come into contact with the metal backing of the patella. Continued metal to metal contact, as the knee is flexed, results in abrasion and scratching. The surface roughness of the two face to face metal components continues to worsen and eventually results in an intolerable level of discomfort for the wearer. Surface scratching and abrasion of the components can also significantly reduce the strength and fatigue resistance of the implant system as a whole.
Heretofore, it has generally been necessary, even in the case of an otherwise well-fixed and well-aligned total knee femoral component, to remove and replace the rigidly implanted metal prosthesis. Revision of one or more total knee replacement components, particularly the femoral component, is a traumatic procedure and the weakened support structure resulting from bone loss which frequently occurs during total revision arthroplasty makes such procedure undesirable.
Until now, however, there were no other options.
For further background, reference is made to an article entitled "Laser and SEM-Polished Femoral Components: `Like New`" which appeared on pages seven and eight of CONVENTION HIGHLIGHTS, American Academy of Orthopaedic Surgeons 60th Annual Meeting, Volume 12: February 1993, Published by Academy Professional Information Services, Inc., San Francisco, Calif., a copy of which is provided in the Information Disclosure Statement filed with the present application. It is to be noted that at the end of the article, the name Tom Fisk, BS, appears. This Tom Fisk is one of the co-inventors in the present application.